The invention relates to interposer assemblies of the type which are sandwiched between substrates to form electrical connections between opposed pairs of pads on the substrates.
U.S. Pat. No. 6,290,507, assigned to InterCon Systems, Inc. of Harrisburg, Pa., assignee of the present invention, discloses an interposer assembly including a dielectric plate with passages extending through the plate and metal spring contacts located in the passages for forming electrical connections between pads on opposed substrates. The contacts are stamped from thin strips of sheet metal, plated and then inserted into the passages to form electrical circuit paths extending through the thickness of the plate between pairs of contact pads. Plating of stamped contacts surrounds the contact with a protective plating to reduce contact resistance and prevent corrosion. The portions of the strip left over after stamping of the contacts are waste.
The contacts may be closely spaced from each other on the plate with Xxe2x80x94X and Yxe2x80x94Y spacing of 0.050 inches (1 mm) using a plate having a thickness of 0.048 inches. This interposer assembly has a contact density of 400 to 645 contacts per square inch, depending upon the contact spacing. The contacts reliably establish electrical connections between pairs of contact pads when sandwiched between circuit members.
Interposer assemblies must meet performance standards for given applications, including size and inductance standards. Lower contact inductance permits the interposer assembly to transmit higher frequency signals between substrates.
Particular applications may require thinner plates and contacts spaced closer together than possible using an interposer assembly with spring contacts stamped from sheet metal. Applications using higher speed signals require that the contacts have less inductance than contacts stamped from sheet metal.
It is desirable to reduce the cost of an interposer assembly by reducing the thickness of the plate, the spacing between contacts and the size of the spring contacts in the passages extending through the plate.
Accordingly, there is a need for an improved interposer assembly with reduced plate thickness, more closely spaced spring contacts, less expensive spring contacts, and reduced contact inductance. The improved interposer assembly should be less expensive to manufacture than conventional interposer assemblies.
The invention is an improved interposer assembly with spring contacts mounted in passages extending through a dielectric plate where each contact is formed from a short length of small diameter preplated cylindrical wire. Each contact includes a rounded contact nose on each side of the plate for forming wiped high-pressure electrical connections with opposed contact pads.
The spring contacts are formed from preplated conductive wire preferably having a diameter of 0.004 to 0.005 inches. Contacts are cut from a continuous length of preplated wire without waste and are shaped immediately prior to insertion into the plate without the need to post-plate the contacts. The contacts are confined in passages in a thin plate having a thickness of as little as 0.025 to 0.035 inches with Xxe2x80x94X and Yxe2x80x94Y spacing between adjacent contacts of 0.032 inches or less. The improved interposer assembly with wire spring contact spacing of 0.032 inches has a contact density of 1000 contacts per square inch. This contact density is considerably greater than the 400 to 645 contacts per square inch density of interposer assemblies using spring contacts stamped from sheet metal. The wire contacts reliably establish electrical connections with contacts or opposed substrates.
Miniaturization of the interposer assembly, elimination of waste and post-plating and insertion of spring contacts into through passages immediately after shaping reduces the cost of manufacture and assembly without sacrificing reliability.
Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings illustrating the invention, of which there are four sheets of drawings and one embodiment.